Olympic hopeful Elizabeth Lamb extended her unbeaten record in trans-Tasman high jump competitions this summer but unhelpful weather conditions in Melbourne have stymied her attempt to clear the qualifying mark required for London.

Lamb added the Melbourne Track Classic title to her collection in an event which doubled as Australia's selection trials for London 2012, but her winning height of 1.83-metres was well short of the 1.95m she needs to compete at her first Olympics.

With the selection cut-off on July 8, Lamb still has plenty of opportunities to make the qualifying standard and for starters will be hoping for friendlier conditions when the New Zealand track and field championships are held in Auckland from March 23-25.

She recorded her personal best of 1.90m in Hamilton last month, 2cm short of the national record.

Olympian Stuart Farquhar renewed his rivalry with Commonwealth champion Jarod Bannister and again finished second best to the Australian, whose best of 82.97m was exactly 2m superior.

Tom Walsh, New Zealand's second-ranked shot putter behind teenage sensation Jacko Gill, took bronze in his event with a best of 18.11m, one of his most impressive efforts of the season.

Kenya-based Waikato 5000m metre runner Jake Robertson was fourth in his pet event, the first he has run in the southern hemisphere since relocating to Africa.

The 22-year-old positioned himself near the front of the field for most of the 12-1/2 laps and with three laps to go sat comfortably in third, behind Collis Birmingham and Olympian Craig Mottram.

But the two Australians pulled clear over the last 800m before Mottram prevailed while Robertson was denied a place on the podium by American Ben True. Robertson's time of 13min 27.91sec was the second fastest of his career but almost 8sec outside the time required to be considered for London.

Meanwhile, Camille Buscomb was unable to preserve her unbeaten record this year in the 1500m, her personal best of 4min 19.66sec was only good enough for seventh in a high quality field.

Sprinter Monique Williams continues to struggle in her comeback from injury and could only manage sixth in the 200m final in 24.75sec, well adrift of her personal best of 22.90sec.

The Delhi Commonwealth Games finalist has only raced sparingly since India and needs 23.00sec to qualify for London.

New Zealand 100m hurdles champion Fiona Morrison finished fourth in her final in 13.88 seconds behind world champion Sally Pearson, an overwhelming favourite to win gold in London.